1. Field of the Invention
The invention relates to rollers for paper folding machines and more particularly to such a roller with a resilient ribbed end to end surface for self cleaning.
2. Description of the Prior Art
In folding machines it is important that the sheets of paper to be folded are advanced precisely and without slippage or delay. Some of the paper stock that is folded varies in finish, weight and composition and may have a paper dust and offset press spray binder coating material on the surface which often causes problems with many of the rollers currently in use. A common roller for paper folding is of cylindrical configuration of steel and with transverse grooves. The surface coating material and the paper tends to dull the grooves in the rollers.
The U.S. Pat. to Wolstenholme, No. 1,793,202, shows a roller for applying color or printing fluid to the surface of a printing roller. The Wolstenholme roller uses an aluminum cylinder covered with a layer of rubber with intersecting grooves to form protuburances but does not have the ribbed resilient surface of my invention, is intended to retain material therein rather than being self cleaning, and would not be suitable for use with paper folding machines.
The U.S. Pat. to Tifft, No. 2,434,820, shows a loom temple roller formed of a core of wood with a cylindrical sleeve wrapped therearound and slit end to end. The Tifft roller would not properly advance paper sheets for folding and would tend to accumulate debris.
The U.S. Pat. to Weiler, No. 3,332,131, shows a sleeve for fiberglass resin rollers which has a coarse spiral groove extending end to end. The Weiler roller surface is rigid, would not be suitable for advancing sheets of paper for folding and suffers from other shortcomings.
The U.S. Pat. to Odiorne, No. 3,447,221, shows a roller structure and method of manufacture that involves a knurled metal core covered with an elastomer that is ground to uncover the peaks of the knurling. The Odiorne structure is expensive, would have a short service life and suffers from other shortcomings that would preclude its use with paper folding machines.
The U.S. Pat. to Clerx et al., No. 3,937,919, shows a fixing device which includes an elastic roller with surface grooves or ribs that have a scraping knife associated therewith to prevent sticking. The Clerx et al. structure is not suitable for paper advance for folding.
The U.S. Pat. to Zavodny, No. 4,016,811, shows a grooved roller of metal which has closely spaced spiral grooves for pick up of the fluid to be transferred. The roller of Zavodny is formed of metal treated to be water receptive, lacks resiliency at its surface and accordingly is not self cleaning and would not be suitable for paper advance for folding.
It has also been proposed to employ smooth surfaced rubber rollers but these have a tendency to accumulate debris and particularly offset press spray barrier which renders them unsatisfactory.
It has also been proposed to provide rollers having circumferential longitudinally grooved or knurled metal sections with interposed rings of smooth surface urethane but these rollers also have a tendency to collect debris including offset press spray barrier which renders them unsatisfactory.
The structure of my invention provides a roller with a resilient outer surface having flat outer faces separated by helical grooves that provide superior sheet advance and control and improved gripping capabilities, does not clog with debris, and has other advantages.